CMOS image sensors capture light and convert it into digital images using millions of tiny pixels, each acting as a light-sensing unit.
At their core, CMOS (Complementary Metal-Oxide-Semiconductor) image sensors utilize an array of pixels, where each pixel contains transistors, including a photodiode and an amplifier. This structure allows for individual pixel processing.
Here's a breakdown of the process:
- Light Capture: When light hits the sensor, the photodiodes accumulate electrical charge when exposed to light. The amount of charge accumulated is directly proportional to the intensity of the light received by each pixel.
- Charge Conversion: those charges are then converted to voltage. This conversion happens within each pixel's circuitry.
- Signal Amplification: The resulting voltage signal is amplified within the pixel itself. This in-pixel amplification helps to improve the signal-to-noise ratio and allows for faster readout compared to older technologies.
- Transmission: Finally, the amplified voltage signals from each pixel are transmitted as electrical signals to the sensor's output circuitry for further processing, such as analog-to-digital conversion and image formation.
Unlike CCD (Charge-Coupled Device) sensors, which move charge across the chip and read it at a few output nodes, CMOS sensors read out the voltage signal from each pixel individually. This architecture enables features like faster frame rates, lower power consumption, and the ability to integrate more functions onto the sensor chip itself.
Key Components per Pixel:
- Photodiode: Converts light into an electrical charge.
- Transistors (including Amplifier): Convert the charge to voltage, amplify the signal, and facilitate pixel readout.
Benefits of CMOS Sensors:
- Faster readout speeds
- Lower power consumption
- Reduced manufacturing costs
- Ability to integrate control and processing circuitry on the same chip
This fundamental process of light capture, charge accumulation, voltage conversion, amplification, and signal transmission forms the basis of how CMOS image sensors capture the world around us in digital form.
